OBJECTIVES: The short term goal of our research is to investigate the metabolism of the inhalational anesthetics halothane, ethrane, methoxyflurane and isoflurane in laboratory animals. The ultimate objective of our research is to investigate the metabolism of the inhalational anesthetics in humans once preliminary studies have been completed in animals. In our initial studies we would like to determine which of the several forms of cytochrome P-450 is responsible for the metabolism of a given anesthetic. Then using the purified enzymes we hope to elucidate the structure of the anesthetic metabolites and the stoichiometry of metabolite production. In order to demonstrate that the anesthetic metabolites produced in vitro are also produced in vivo, we will attempt to establish their presence in the urine of patients anesthetized with a particular anesthetic, if this has not already been established. We are also interested in investigating the alterations which occur in liver microsomal proteins, especially the cytochromes P-450, after induction by the inhalational anesthetics and phenobarbital. These changes in microsomal proteins are expected to be major determinants of the metabolism and activity of a wide variety of endogenous substrates, e.g., prostaglandins, bile acids, and exogenous substrates, e.g., carcinogens, anesthetics, drugs, and can determine the variability in individual responses to an anesthetic or drug. METHOD: High resolution two-deminsional polyacrylamide gel electrophoresis will be used to analyze the quantitative and qualitative alterations occurring in liver microsomal cytochromes P-450 and other proteins following induction by the anesthetics and phenobarbital. The anesthetic metabolites fluoride ion and fomaldehyde will be measured with fluoride ion specific electrode and a sensitive colorometric assay, respectively. Since all of the inhalational anesthetics to be investigated are probably metabolized to haloacids, an assay will be developed to quantitate picogram quantities of these haloacids. Unequivocal identification of metabolites will be determined in a mass spectrometer interfaced to a gas-liquid chromatograph. The proteins cytochrome P-450 and cytochrome P-450 reductase will be purified as described in published procedures.